alpha-Galactosylceramide (
alpha-GalCer) is a
glycolipid that stimulates natural killer T cells to produce both T helper (Th) 1 and Th2
cytokines. This property enables
alpha-GalCer to ameliorate a wide variety of infectious, neoplastic, and
autoimmune diseases; however, its effectiveness against any one disease is limited by the opposing activities of the induced Th1 and Th2
cytokines. Here, we report that a synthetic
C-glycoside analogue of
alpha-GalCer, alpha-
C-galactosylceramide (
alpha-C-GalCer), acts as natural killer T cell
ligand in vivo, and stimulates an enhanced Th1-type response in mice. In two disease models requiring Th1-type responses for control, namely
malaria and
melanoma metastases,
alpha-C-GalCer exhibited a 1,000-fold more potent antimalaria activity and a 100-fold more potent antimetastatic activity than
alpha-GalCer. Moreover,
alpha-C-GalCer consistently stimulated prolonged production of the Th1
cytokines interferon-gamma and
interleukin (IL)-12, and decreased production of the Th2
cytokine IL-4 compared with
alpha-GalCer. Finally,
alpha-C-GalCer's enhanced therapeutic activity required the presence of
IL-12, which was needed to stimulate natural killer cells for optimal
interferon-gamma production, but did not affect
IL-4. Overall, our results suggest that
alpha-C-GalCer may one day be an excellent therapeutic option for diseases resolved by Th1-type responses.